In general, an air conditioner is an apparatus which cools or heats an indoor space by performing a process of compressing, condensing, expanding, and evaporating a refrigerant.
Recently, as energy saving measures to address global warming have been implemented, various methods for effective energy consumption of conventional energy consumption apparatuses have been proposed.
As to such energy saving, methods of controlling air conditioners in which the number of human bodies or movement of human bodies located within an indoor space is sensed and temperature is controlled thereby have been proposed.
Conventional air conditioners are classified into two types, as detailed below, according to human body sensing methods.
First, a triangular method is a method of calculating the position of an object by measuring distances from pre-defined reference points. As the triangular method, there are an active badge system using infrared light, an active bat system using ultrasonic waves, and an easy living system using a vision system.
Next, a proximity method is a method of determining a position using proximity to a known reference point. As the proximity method, there is a smart floor system using a pressure sensor and an automatic ID system using RFID.
Further, human body sensing devices may be divided into a terminal based method, such as an active bat system, and a non-terminal based method using a vision sensor or a pressure sensor according to whether or not a resident possesses a terminal.
In case of the terminal based method using infrared light or ultrasonic waves, the position of a resident is not searched but the position of a terminal possessed by a resident is searched. Thereby, only if a resident possesses a terminal at all time in an indoor space, the position of the terminal of the resident may be recognized.
On the other hand, an easy living system using a vision system may cause privacy violation in home, and a smart floor system using a pressure sensor may have poor scalability and a difficulty in management.
As human body sensors which have been used or developed now in security, home electronics, and lighting, passive infrared sensors (PIR), which directly generate electrical signals in response to external heat sources, are employed. These conventional human body sensors are motion sensors which may sense a human body present within a sensing area only if the human body moves, and such a PIR sensor senses infrared light of 8˜12 μm emitted from a human body when the human body moves. Then, the PIR sensor converts received light energy, changed when the PIR sensor senses infrared light, into an electrical signal and may thus recognize the human body moving within a sensing range.